General studies of intrarenal catecholamine-containing nerves have shown that these sympathetic nerves form dense plexuses around the renal arteries and veins. Intrarenal sensory nerves are both chemoreceptive and mechanoreceptive, but data on receptor distribution are minimal and the fine structure of sensory terminals and the neurotransmitters used by these nerves are unknown. The investigator has examined with the electron microscope, a new intrarenal structure consisting of a cluster of axonal enlargements that partially surround arterioles and contain catecholamine in high concentration. Functionally, axons of this neurovascular structure may be efferent or afferent. The objectives of the proposed project are to study the anatomical relationships between intrarenal axonal enlargements and the renal arterial tree. Localization of sensory and autonomic nerve cell bodies innervating the kidneys and systematic section of their axons will help to establish the sensory or autonomic nature of the neurovascular structure. Immunohistochemical localization of TH, DBH, substance P, somatostatin and VIP will help to characterize the neurotransmitter used by these nerves. These data will be useful in the process of determining whether the modified axons and associated arterioles contribute significantly to renal function in healthy or in hypertensive animals.